The present invention relates to apparatus for transferring an object, such as a label, from a pickup point to a delivery point. In particular, the present invention relates to a linear actuator for transporting a label transfer device from a label supply means such as a magazine to a distal location, such as the interior of a mold cavity of a molding machine.
The present invention is an improvement of the invention disclosed in application Ser. No. 544,986, filed Oct. 24, 1983 for IN-MOLD LABEL TRANSFER APPARATUS by the same inventors, that application being incorporated herein in its entirety by reference. That application also discusses the problems and disadvantages existing in the prior art label transferring apparatuses. However, those problems and disadvantages will be summarized herein for convenience.
It is known to apply a label to a plastic container that is made by blow molding by applying the label inside the mold. Previous arrangements for supplying the labels into the mold are depicted, for example, in the U.S. Pat. Nos. Dickinson 3,324,508, Borkman 3,292,209, Hellmer 4,355,967 and 4,359,314, and Hellmer et al 4,397,625. These references are discussed in the afore-mentioned patent application.
While the prior art does recognize the basic concept of supplying labels at one location and transferring those labels into an open mold at another location, the devices of the prior art suffer from certain disadvantages. Generally, the aforementioned patents disclose label transferring and applying machines having complex structures that are incapable of modification so as to permit their incorporation into conventional, installed mold machinery. Furthermore, the prior art devices do not permit very rapid, yet accurate transferring and positioning of the labels.
The successful, rapid and accurate positioning of a label inside the mold of a molding machine requires the interrelated, cooperative aspects of several components. Of particular importance is the accurate positioning in the transverse, longitudinal and rotational planes of a label transfer mechanism from a first location where a label supply means provides a label to be picked up by the transfer mechanism to a second location where the label is to be deposited such as in the mold cavity of a molding machine.
The problems become even more difficult when the requirement is added that the label delivery apparatus must be designed with flexibility so that it can be incorporated into a number of different types of previously installed molding apparatuses. The requirement for component flexibility also means that the individual components must work separately and in combination in a variety of orientations and in a variety of machinery environments.
The critical interrelationships between the label pickup means and the label supplying means becomes even more important when high label transfer speed and accurate label positioning are required. Consistent accuracy can be achieved if the label transfer mechanism has a simplistic motion and it has to travel a minimal distance. In all of the devices of the aforementioned Dickinson, Borkman, Hellmer and Hellmer et al patents, there is a transverse component of movement between the transfer head and the label both at the moment of pickup of the label and at the moment of transfer of the label to the mold cavity. That transverse component of motion tends to "scuff" the label as it is being transferred, thereby possibly damaging the label and certainly minimizing the ability to perfectly position the label on the label transfer head and within the mold cavity. A simple motion of the transfer head is also dictated in order to permit the retrofitting of a label transfer mechanism to installed molding machines. Therefore, accuracy and speed of label transfer are increased with an increase in the simplicity of label pickup motion and a reduction in the distance of travel.
When considering the further problems of retrofitting an in-mold label application system into an existing, operating molding machine, the existing prior art devices become impossible to modify. The principal reason is that existing molding machines have limited access space both for inserting the label and for installing the label transferring device and the label storage means. Quite often, tnere is a small area into which an extensible label transfer head can be inserted from a distal location. The problem, however, is that the inserted device cannot be supported close to the mold and therefore must be mounted in a cantilever fashion. As is well known, it is very difficult to accurate position a heavy object over an extended distance when that object has been mounted by a cantilever mounting.
Hence, there exists a need for further improvements in apparatus for transferring labels from a label supply means to a mold cavity such that the label can be accurately, yet rapidly transferred and positioned.